Revisiting self-interference in Young’s double-slit experiments

Abstract

Quantum superposition is the heart of quantum mechanics as mentioned by Dirac and Feynman. In an interferometric system, single photon self-interference has been intensively studied over the last several decades in both quantum and classical regimes. In Born rule tests, the Sorkin parameter indicates the maximum number of possible quantum superposition allowed to the input photons entering an interferometer, where multi-photon interference fringe is equivalent to that of a classical version by a laser. Here, an attenuated laser light in a quantum regime is investigated for self-interference in a Mach–Zehnder interferometer, and the results are compared with its classical version. The equivalent result supports the Born rule tests, where the classical interference originates in the superposition of individual single-photon self-interferences. This understanding sheds light on the fundamental physics of quantum features between bipartite systems.

Coherently driven quantum features using a linear optics-based polarization-basis control

“…To provide random polarization bases of a single photon, the laser L is followed by a 22.5°-rotated half-wave plate (HWP). Using neutral density filters, the randomly polarized photons are maintained at a low mean photon number state, satisfying independent measurement-based statistics [31]. For the phasematched coherent photon pairs, a set of acousto-optic modulators (AOMs) are used in both paths of the noninterfering Mach-Zehnder interferometer (NMZI), where the AOMs are synchronized and oppositely scanned each other for a given bandwidth ∆.…”

Coherence interpretations of nonlocal quantum correlation based on a quantum eraser

“…The cost to pay for this nonlocal fringe is a 50% measurement-event loss. The orthogonal polarization basis-product superposition between paired photons indicates a new concept of the second-order amplitude superposition, which is different from the conventional firstorder amplitude superposition in single photon's self-interference [16,24].…”

“…As shown in the Inset, the AOM is set for a double-pass scheme for 𝛿𝛿𝑓𝑓 𝑗𝑗 -independent propagation direction. By coincidence detection, only doubly-bunched photons are selectively chosen from the attenuated laser [35]. In this case, 50 % of non-split (bunched) photons by the first BS are discarded by coincidence detection.…”

“…However, the nonlocal fringe in the quantum eraser is still mysterious due to the second-order amplitude superposition resulting from independently measured local intensities. This mysterious phenomenon of the second-order amplitude superposition is different from the quantum mystery in the first-order amplitude superposition of a single photon's self-interference [16,21,24]. Such nonlocal second-order amplitude superposition can be erased by the delayed choice for a definite (distinguishable) slit, resulting in the particle nature of photons.…”

“…For this, a mean consecutive photon distance is set to be much longer than the laser's coherence length. For the coincidence measurements, however, only Poisson-distributed doubly bunched photons are post-selected for the nonlocal feature at ~1 % ratio of single photons [35]. Unlike SPDC-based entangled photons, whose frequencies are oppositely detuned across the center frequency 𝑓𝑓 0 , coherent photons from L have no such detuning relation due to the cavity optics.…”